Migrate Verifier and AbstractMavenIntegrationTestCase to NIO2

This commit migrates the Maven integration test infrastructure from java.io.File
to NIO2 Path API while maintaining full backward compatibility.

Changes in Verifier class:
- Added Path-based overloads for loadProperties(), loadFile(), filterFile()
- Migrated file operations to use Files.* methods instead of FileUtils
- Replaced FileUtils.deleteDirectory() with custom NIO2 implementation
- Updated file verification methods to use Path and DirectoryStream
- Removed dependency on org.codehaus.plexus.util.FileUtils

Changes in AbstractMavenIntegrationTestCase class:
- Added extractResourcesAsPath() method returning Path instead of File
- Updated settings file handling to use Path operations

Benefits:
- Better performance with NIO2 operations
- Improved error handling and cross-platform compatibility
- Modern API usage while maintaining backward compatibility
- Comprehensive test coverage for new functionality

All existing integration tests continue to work without modification.
New @SInCE 4.0.0 methods provide Path-based alternatives for modern usage.

Author: gnodet

its/core-it-support/maven-it-helper/src/main/java/org/apache/maven/it/AbstractMavenIntegrationTestCase.java

@@ -23,6 +23,8 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.PrintStream;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Arrays;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
@@ -72,10 +74,21 @@ public void close() throws IOException {}
 
 
     protected File extractResources(String resourcePath) throws IOException {
-        return new File(
-                        new File(System.getProperty("maven.test.tmpdir", System.getProperty("java.io.tmpdir"))),
-                        resourcePath)
-                .getAbsoluteFile();
+        return extractResourcesAsPath(resourcePath).toFile();
+    }
+
+    /**
+     * Extracts test resources to a temporary directory.
+     *
+     * @param resourcePath The path to the resource directory, must not be <code>null</code>.
+     * @return The path to the extracted resources, never <code>null</code>.
+     * @throws IOException If the resources could not be extracted.
+     * @since 4.0.0
+     */
+    protected Path extractResourcesAsPath(String resourcePath) throws IOException {
+        return Paths.get(System.getProperty("maven.test.tmpdir", System.getProperty("java.io.tmpdir")))
+                .resolve(resourcePath)
+                .toAbsolutePath();
     }
 
     protected Verifier newVerifier(String basedir) throws VerificationException {
@@ -107,27 +120,27 @@ protected Verifier newVerifier(String basedir, String settings, boolean createDo
         verifier.setAutoclean(false);
 
         if (settings != null) {
-            File settingsFile;
+            Path settingsPath;
             if (!settings.isEmpty()) {
-                settingsFile = new File("settings-" + settings + ".xml");
+                settingsPath = Paths.get("settings-" + settings + ".xml");
             } else {
-                settingsFile = new File("settings.xml");
+                settingsPath = Paths.get("settings.xml");
             }
 
-            if (!settingsFile.isAbsolute()) {
+            if (!settingsPath.isAbsolute()) {
                 String settingsDir = System.getProperty("maven.it.global-settings.dir", "");
                 if (!settingsDir.isEmpty()) {
-                    settingsFile = new File(settingsDir, settingsFile.getPath());
+                    settingsPath = Paths.get(settingsDir).resolve(settingsPath);
                 } else {
                     //
                     // Make is easier to run ITs from m2e in Maven IT mode without having to set any additional
                     // properties.
                     //
-                    settingsFile = new File("target/test-classes", settingsFile.getPath());
+                    settingsPath = Paths.get("target/test-classes").resolve(settingsPath);
                 }
             }
 
-            String path = settingsFile.getAbsolutePath();
+            String path = settingsPath.toAbsolutePath().toString();
             verifier.addCliArgument("--install-settings");
             if (path.indexOf(' ') < 0) {
                 verifier.addCliArgument(path);